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MEE 312 – Engineering Materials
Due Monday, April 3 in class
1) Briefly (in a single phrase or short sentence) describe/define the following terms in your own words and, if relevant, include an example:
- Solid solution f) Hume-Rothery rules
- Phase g) Freezing range
- Gibbs phase rule h) Tie line
- Unlimited solubility i) Lever rule
- Limited solubility
2) How does a binary phase diagram differ from a unary phase diagram? When a binary phase diagram is referred to as “isomorphous,” what does that mean?
3) In the context of a binary phase diagram, how does the composition of a phase differ from the amount of a phase?
4) Based on the Hume-Rothery rules, which alloy would you expect to have unlimited solid solubility? (Hint: Consult Appendices A and B in your textbook, and make sure you understand which of the H-R rules are violated for the alloys below with limited solubility.)
- Cu-Zn alloy
- Al-Cu alloy
- Mg-Zn alloy
- Au-Ag alloy
5) Use the following phase diagram for a NiO-MgO ceramic to answer the following questions:
- This phase diagram is best classified as
- Unary and isomorphous
- Binary and isomorphous
- Binary and polymorphous
- Ternary and polymorphous
- The liquidus temperature for NiO-20% MgO is
- Lower than NiO-40% MgO
- Higher than NiO-40% MgO
- The same regardless of composition
- The same as the solidus temperature for NiO-20% MgO
- Estimate the solidus temperature, liquidus temperature, and freezing range for a NiO-60% MgO alloy.
- The freezing range is largest for ______________, and smallest for _______________
- If we wanted to heat treat (anneal) a solid ingot of NiO-50% MgO alloy to enhance its ductility, we would need to do so below what temperature and why?
- Use the Gibbs phase rule to prove that there are two degrees of freedom in the regions of the phase diagram where only the liquid L or solid S phase is present, and one degree of freedom in the two-phase (L + S) region. Which form of the Gibbs phase rule will you use to prove this, and why?
- For NiO-60% MgO, determine the phases present at each of the following temperatures:
- 2200 ◦C
- 2500 ◦C
- 2700 ◦C
Then, at each temperature, estimate (i) the composition of each phase and (ii) the amount of each phase.
- Describe the evolution of the composition of NiO-60% MgO as it is cooled from a molten liquid at 2700 ◦C, through the two-phase region, to a solid ceramic at 2200 ◦C.
- In general, what would you expect to happen to the mechanical properties (e.g., strength and ductility) of a NiO-MgO ceramic as you increase the mol % NiO?
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